Extensive data from neurophysiological studies indicate that important receptor mechanisms mediating proprioception (information about limb position and movement) lie in the joint capsule. The major objective of the present research is to systematically assess the nature of the presumed proprioceptive deficit prior to and following joint replacement arthroplasty, a procedure in which the capsule is released and removed. The rationale is as follows: First, the proprioceptive contribution following joint replacement has not been charted, either clinically or experimentally, in spite of its likely relationship to recovery of motor function. Second, the selective removal of capsular afferent information by surgical intervention affords direct inferences on the function of receptor mechanisms relaying movement-position feedback to the central nervous system. Our initial experiments have shown that perception and production of various joint angles is preserved in joint replacement patients. Joint afferent information may not provide dimension-specific input to the central nervous system but may play a 'tuning' function on the parameterization of muscle-joint linkages. Our new experiments explore the dynamic organization of voluntary movement in joint replacement patients in order to examine the 'tuning' view in more detail.